I find strange nobody has tried to create weapons able to kill monsters... I mean, look at Demon Cyborg's plasma beams... if somebody made guns with that power, the army could kill 99 % of monsters with no trouble at all (they would need to make them in way that the output could be graduated with great precission, to avoid somebody blasting a city block, of course...).
I know the Hero Association has a policy of "sending chumps to fight monsters and promoting the survivors" instead of spending money in giving their troops some serious training and equipment, but the army/self-defense forces should research weapons able to defeat monster threats...